Rollers are used in many industries for flattening and shaping sheets of various materials. The process of drawing steel or similar materials into flat sheets or rolls requires that the material be run through a series of rollers. Similarly the process for making paper requires that the product be run through a series of rollers. The industry refers to this series of rollers as a "roll mill". The roll mill process is also used to form pipe, wire, and other similar products.
A roll mill consists of a series of pairs (or sets) of parallel rollers generally having a top and bottom roller. These rollers are mounted on movable bearings in such a manner that each roller may be raised or lowered and so that each roller may be moved in a transverse horizontal plane. Each of the rollers in a pair must be aligned in the vertical and horizontal transverse planes with each other and each of the roller pairs must be precisely parallel to each other throughout the sheet path. If there is any mis-alignment, then the formed product will be thicker at one edge or the product will be forced to one side of the roll mill.
Each roll mill will have a different set of requirements. For example, in a (sheet or plate) steel roll mill, each set of rollers must be precisely aligned and all of the rollers must be centered at the same elevation. In order to vary the thickness of the product, the separation of each roller pair is varied. This change in separation is accomplished by adjusting the roller bearing mounts which requires precise alignment after the separation distance is varied. In a paper roll mill, product changes rarely occur and the center of the roller sets do not have to be at the same elevation. However, alignment in the vertical and horizontal planes and parallelism between sets of rollers is still very critical. Roll mill rollers become worn, bearings become damaged, and myriad other maintenance problems will occur in a roll mill, requiring that rollers be removed, repaired and etc. Each time a roller is maintained or moved, then that roller must be aligned.
Roller pairs (or even a single roller) are generally aligned by placing a target (a sighting scale) at both ends of the roller and in contact with the roller. The positioning of the target is critical and the present art requires that the target be placed in a precise horizontal direction whenever the roller is being checked for horizontal alignment and then in a precise vertical direction whenever the roller is being checked for vertical alignment. The placement techniques are well established, but require that optical alignment equipment be able to see (or sight) the target. This often requires that other equipment must be removed from the roll mill. Very often other rollers must be removed which requires that those removed rollers be re-aligned after they are replaced. This makes for a long involved process which can introduce additional mis-alignment problems.
Alignment of rollers is undertaken by taking a sight on the roller target with precision optical equipment and recording the difference in scale readings between the two ends. It should be noted that classical optical techniques or precision laser optical techniques can be used to take such a "sight". The difference in the two readings is the total amount of mis-alignment. Adjustments will then be made and the roller target re-sighted. This process is repeated for the other axis. The process of sighting and adjustment is repeated until the alignment is within tolerance.
A similar process is used to align large rotating equipment such as steam turbines and electric power generators. A sight is taken on the turbine shaft and a sight is taken on the generator shaft. The two pieces of equipment are moved until the shafts are precisely aligned at which time mechanical attachment of the two shafts is made. Shaft and roller alignment techniques are well known in the prior art and the prior art has a long history.